It is known to increase the size of an electro-optic imaging device such as a flat panel display or an image sensor by forming the device using a plurality of tiles, each tile having a two dimensional array of pixels; see for example U.S. Pat. No. 6,262,696 issued Jul. 17, 2001 to Seraphim et al. Large tiled displays can also be made using an array of fiber optic panels in association with smaller displays. The fiber optic panels reduce the edge gap between the display tiles as described in U.S. Pat. No. 4,299,447 issued Nov. 10, 1981 to Soltan et al. WO 99/41732, Matthies et al., published Aug. 19, 1999, describes forming a tiled display device from display tiles having pixel positions defined up to the edge of the tiles. One example of the use of tiles to increase the size of an image sensor is shown in U.S. Pat. No. 5,572,034, issued Nov. 5, 1996 to Karellas.
However, construction of tiled imaging devices is difficult. No two tiles, whether used alone or with fiber optic face plates, are precisely alike and the human eye is extremely sensitive to differences in color, brightness, and contrast in localized areas. There are calibration techniques by which the uniformity and color balance of a display or image sensor tile can be adjusted, but these are difficult, require re-adjustment over time, and are often inadequate. Moreover, the seams between the tile edges are very noticeable as the human eye is very sensitive to straight horizontal and vertical lines.
The assembly of flat-panel tiles is also a problem. In order to ameliorate the problems associated with tile seams, the tiled displays must be assembled very carefully and with great precision. This process is expensive and slow and products are prone to fall out of alignment over time without expensive forms or brackets to align the tiles once they are placed.
There is a need therefore for a tiled electro-optic imaging device that reduces the visibility of tile non-uniformities and tile seams, and that enhances the mechanical assembly of the tiles.